In recent years, an image transmission system connected to a network is widely used in a monitoring camera system and the like. Moreover, the applications for the future are being contemplated, such as an application in which a plurality of cameras mounted on an automobile are connected via a digital network and utilized in a driving assistance system.
In the above-described example, in order to improve the visibility in a light and dark portion and improve the recognizability of a fine shape, a high-gradation image whose gradation is expanded from the gradation of a conventional 8-bit precision YUV signal needs to be used.
When such high-gradation image data is transmitted under limited transmission band conditions of a network or the like, for example by sampling and encoding the YUV components of an original image at 12 bits, the gradation expression of the original image will be improved while the amount of encoding will be increased. Therefore, a technique is desired for efficiently reducing the amount of encoding by encoding while maintaining the number of gradations of an original image as much as possible.
JP-A-2005-252556 (Patent Literature 1) is one of the background art documents of the technical field.